Tara Costa, who was a finalist on "The Biggest Loser" in 2009 after losing 155 pounds, is being sued by a fitness company, FC Online, who claims she has gained 45 pounds- "far too much weight" for her to continue as their brand ambassador. She is being sued by the company for unspecified damages.

(PHOTO:REUTERS/Rick Wilking)

Guests work out before dawn at the Biggest Loser Resort in Ivins, Utah September 6, 2010. Guests at the resort affiliated with the popular reality television show work out in an aerobics room, a gym and a swimming pool for 6 to 7 hours each day. Picture taken September 6, 2010.

Tara Costa's problems with her weight started some time after she appeared on NBC's "The Biggest Loser" and catapulted to fame. In 2011, she was hired by the company and given $45,000 to make appearances at FC locations. However Michael Parrella, the chief executive of the company, alleges she gained too much weight to function as a spokesperson.

"We hired Tara Costa in 2011 to be a spokesperson," Parrella told Newsday. "She came on at a certain weight. We had a fitness clause. She was in material breach after she gained, in my opinion, about 45 pounds. She was supposed to visit 15 of our franchise locations, but we weren't able to send her anywhere because she gained a lot of weight."

Parella also alleged that Costa signed with a competing company, Anytime Fitness, and did not complete her social media contract with them because of the weight she gained.

The same year, Costa appeared on "The Biggest Loser" as a guest and had gained 22 pounds since her initial time on the show. She also admitted in 2012 that she suffered from food addiction, and that her mind is more the problem than her body.

"Now it's not about willpower, it's about- there might be something wrong up here (her mind)," she told ABC News, admitting that she used to eat meals "around 6,000 calories, if not more."

Now Costa has filed suit against FC Online in New York for a breach of contract fees and her lawyer claims she gained no weight.

"Ms. Costa hasn't gained any weight," her attorney Darren Heitner told Newsday. "If that were true and if the public realizes this, then why did they continue to use her image?" he asked, referring to her face being used on ILoveKickboxing.com.

"My client was willing, available and actually excited to fulfill the terms of the appearance contract. It was no one's fault but FC Online's that those appearance opportunities were not presented to her," he added, also denying that Anytime Fitness was a competing company.